An armed militia took over a building at a national wildlife refuge in Oregon late Saturday and vows to occupy the outpost for years to protest the federal government’s treatment of a pair of ranchers facing prison time.

The occupation of a portion of the Malheur National Wildlife Refuge 30 miles southeast of Burns, Ore., followed a peaceful march for ranchers Dwight Hammond, 73, and Steven Hammond, 46, who are scheduled to report to federal prison in San Pedro, Calif., on Monday after being convicted of arson, according to the Oregonian.

Prosecutors said the father and son set the fire, which burned about 130 acres in 2001 on leased federal land, to conceal poaching, according to CNN. The Hammonds argued that they were attempting to reduce the growth of invasive plant species and ward off potential wildfires. The pair was sentenced to five years in prison.

Among the occupiers are several members of the Bundy family, whose patriarch — Nevada rancher Cliven Bundy — was involved in an armed standoff with government agents over grazing rights in 2014.

At a news conference on Sunday, Ammon Bundy said militia members had taken over an unoccupied site. He said the group had not heard from law enforcement and had no desire to be aggressive. He urged other citizens from across the country to join their effort and said that if violence occurred, it would begin on the government’s side.

“If they did,” he said, referring to the authorities taking violent action, “it would simply be over a building that they would come in and kill.”

The federal property, managed by the U.S. Fish and Wildlife Service, was closed and unoccupied for the holiday weekend, the Oregonian reported.

Noting that the group isn’t holding hostages, Ryan Bundy echoed his brother, telling the Oregonian that the group doesn’t want to resort to violence but will not rule it out if authorities attempt to remove the occupiers from the property. He said many of the occupiers would be willing to fight — and die — to reclaim constitutionally protected rights for local land management, according to the Associated Press.

The group is calling for the Hammonds’ release and said the militia was planning an occupation that lasted “for years.”

“The best possible outcome is that the ranchers that have been kicked out of the area, then they will come back and reclaim their land, and the wildlife refuge will be shut down forever and the federal government will relinquish such control,” Ryan Bundy told the Oregonian. “What we’re doing is not rebellious. What we’re doing is in accordance with the Constitution, which is the supreme law of the land.”

One tearful occupier, expecting not to come home, recorded a video railing against the Hammonds’ sentence and saying goodbye to his family. He said he was trying to win the “hearts and minds” of Oregonians.

A message posted on the website of the Malheur National Wildlife Refuge, Jan. 3, 2016. (Screenshot)

The Malheur National Wildlife Refuge was established Aug. 18, 1908, by President Theodore Roosevelt “as a preserve and breeding ground for native birds,” according to the park’s website.

“The Refuge represents a crucial stop along the Pacific Flyway and offers resting, breeding, and nesting habitat for hundreds of migratory birds and other wildlife,” a statement on the site says. “Many of the species migrating through or breeding here are highlighted as priority species in national bird conservation plans.”

At Sunday’s news conference, Ammon Bundy said the refuge’s creation was “an unconstitutional act,” one that removed local ranchers from their lands, thrusting the county into an economic depression.

“This refuge here is rightfully owned by the people and we intend to use it,” he said, adding that they plan to assisting ranchers, loggers, hunters and campers who want to use the land. “We will be here as a unified body of people that understand the principles of the Constitution.”

In a video interview with reporters on Saturday that was posted on his Facebook page, Ammon Bundy said the group is standing up against government “overreach” because “the people have been abused long enough.”

“I feel we are in a situation where if we do not do something, if we do not take a hard stand, we’ll be in a position where we’ll be no longer able to do so,” he said.

A video posted days earlier on Bundy’s Facebook page urged militia members from all over the country to join him:

Harney County Sheriff Dave Ward urged the public to stay away from the area as authorities work to resolve the standoff, according to the Oregonian.

“A collective effort from multiple agencies is currently working on a solution,” Ward said in a statement reported by the paper. “For the time being please stay away from that area. More information will be provided as it becomes available. Please maintain a peaceful and united front and allow us to work through this situation.”

Beth Anne Steele, an FBI spokeswoman in Portland, told the AP that the bureau was aware of the situation at the wildlife refuge, but she declined further comment.

A U.S. Fish and Wildlife Service spokesperson told CNN that the agency and the Bureau of Land Management are monitoring the armed protesters.

“While the situation is ongoing, the main concern is employee safety, and we can confirm that no federal staff were in the building at the time of the initial incident,” the spokesperson said. “We will continue to monitor the situation.”

Cliven Bundy told Oregon Public Broadcasting on Saturday night that he wasn’t involved in the standoff, but he struck a sympathetic tone.

“That’s not exactly what I thought should happen, but I didn’t know what to do,” he said. “You know, if the Hammonds wouldn’t stand, if the sheriff didn’t stand, then, you know, the people had to do something. And I guess this is what they did decide to do. I wasn’t in on that.”

Late Saturday, the occupiers blocked the entrance of the federal headquarters with a pickup truck and placed an American flag over the welcome sign, according to Oregon Public Broadcasting. An Oregon State Police car “idled by the side of the road just outside Burns,” the broadcaster reported, but there were no signs of a larger law enforcement presence in the area.

“We are not hurting anybody or damaging any property.,” Ammon Bundy told OPB. “We would expect that they understand that we have given them no reason to use lethal force upon us or any other force.”

Ron Gainer, the owner of a nearby RV park who dropped off some chili for the occupiers, told the broadcaster that he counted about 15 people, a half-dozen vehicles and a trailer at the site. The estimate differed sharply from the Bundy family accounting, which put the number of people at the refuge at about 150, according to OPB.

By nightfall, the broadcaster noted, the temperature had plummeted to 10 degrees, prompting occupiers to bundle around a campfire. Some of those present identified themselves as nearby residents and supporters of the convicted ranchers.

Asked by an OPB reporter how many militia members were at the headquarters, Bundy didn’t divulge.

BREAKING! SHARE! Standing for the rights of Men & Women. Calling all freedom loving people to come to Harney County Oregon, come to the Malhuer Wildlife Refuge. The people are finally getting some good use out of a federal facility.